1. Field of the Invention
This invention relates to microwave ovens for cooking food, and particularly to a new and improved combination microwave/forced convection oven having a substantially closed cooking container therein and a separate heating element with means for circulating within the container air heated by the element, thus allowing cooking of the food by both convective and microwave heating.
2. Description of the Prior Art
Microwave ovens have become widely accepted in many countries for the cooking of many foods at a fast cooking rate. The microwave frequency energy is radiated within the oven cooking cavity from an energy source such as a magnetron. The waves are radiated and reflected within the oven cavity in free space and may be distributed by such means as mode stirrers, antennas, and the like. The microwave energy sets up a high frequency oscillatory movement of the molecules in the food to cause internal heating by molecular friction.
Microwave cooking, however, often produces no browning or other darkening of the surface of the food being cooked. Both the flavor and appearance, darkening is advantageous. One method for accomplishing this in the past has been to blow excess heat from the magnetron assembly into the microwave oven cavity, thus obtaining a convective heating effect. However, this method may prove unreliable and inefficient in that the amount of heat generated by the magnetron heat source is not readily controllable and the heat is distributed throughout the entire cavity rather than being concentrated in the locality of the food being cooked.
Another method for darkening the surface of food has been by exposing it directly to a radiant heating element located within the microwave cavity. However, this method requires periodic changing of the position of the food to ensure uniform darkening. A further disadvantage of both of the above methods is that the microwave oven itself, which remains at room temperature when only microwave energy cooking is employed, will become heated above room temperature, possibly presenting a safety hazard.
Another problem associated with microwave cooking is that of splatter resulting from escaping vapors and food particles which accumulate on the surfaces of the oven cavity and make cleaning difficult. A solution to this problem has been to place a tightly closed microwave transparent container inside the oven cavity to hold the food while it is being cooked. Although this solves the problem of splatter, the close tightness of the container precludes the use of convective heating as a means of darkening the surface of the food.
The primary object of the present invention is to provide new and improved means for convectively heating food in a microwave oven, and effective for darkening the surface of the food and contributing to the heating thereof, while it is simultaneously being heated by microwave energy.
Another object of the present invention is to obtain in a combination microwave/forced convection oven maximum advantage of the convective heating by confining the heated air to a substantially closed food container positioned within the microwave oven cavity, while at the same time allowing the remaining areas of the oven to remain at approximately room temperature.
Another object of the present invention is to provide in a combination microwave/forced convection oven a heating element of known thermal output and a means of known capacity for moving the air past the heating element, and thus effective for controlling the temperature and amount of convectively heated air in the oven.
Still another object of the present invention is to provide in a combination microwave/forced convection oven, means for confining vapors and food particles, thrown off by the food while it is being cooked, to a closed container.